Do plastic greenhouses work?

Do plastic greenhouses work?

Do plastic greenhouses work, or, put another way, are you able to grow more fruit and vegetables more successfully by using a plastic greenhouse than without? That’s what this blog post will investigate.


Why buy a plastic greenhouse?

Common reasons for buying a plastic greenhouse are to:

  • Germinate seedlings earlier in the year
    Success will depend on how exposed to the elements is the spot where you place your plastic greenhouse. The warmth in a plastic greenhouse comes from the sun. I have found greater success by covering seed trays with plastic film before placing in a plastic greenhouse for extra warmth. If the weather outside is cold, and the growhouse is in a shady position, the temperature inside the growhouse may not be that much different to the outside temperature.
  • Harden off seedlings before planting out
    This can be very successful. Spring weather can be unpredictable, and if you are germinating many types of plants it is common to run out of warm windowsill space. Having the extra room provided by a plastic greenhouse comes in very handy. It also acts to harden the plants off before planting outside.
  • Protect sensitive plants from cold winds, rain and disease
    Disease like tomato blight is significantly more common in wet and cold weather. Once your seedlings are successfully planted out, a plastic greenhouse can also work as an ideal spot for plants like tomatoes, cucumbers and aubergines. In lousy summer days it is often not the air temperature that is particularly cold, but the wind chill, and sensitive plants can benefit from being well protected.
  • Create a better growing environment for heat loving plants
    Apart from disease, heat loving plants will respond better and flower or fruit earlier if they are less concerned with simply survival.

See books on greenhouse growing on

In my experience I would advise against using a plastic greenhouse as an ‘all year round’ growing area outside. Unless you plan to purchase a professional grade polytunnel at a potential cost of hundreds of pounds, then the covers of plastic greenhouses are unlikely to be durable enough for your needs. Similarly, if you position a plastic greenhouse in an exposed area with little protection from the wind, you may find that your plastic greenhouse does not last long. Follow this link to see plastic greenhouses on Amazon UK.

So do plastic greenhouses work … ?

This clearly depends on what you want to do use them for, but my experience is that they are good for:

  • A cheap way of having fun, growing a greater variety of vegetables
  • A more sure way of getting a harvest from sensitive plants like tomatoes and aubergines
  • A great way for hardening off seedlings, and to create more free germinating space on warm windowsills

Comparing a typical plastic greenhouse (ie not professional polytunnel) to a glass greenhouse:

  • They are significantly less durable
  • They are not 365 days a year (for the reason above)
  • They are not suitable for an internal heatsource

I would advise budgeting to replace the plastic cover every 1 to 3 years. See plastic greenhouses on Amazon UK.



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